The invention is in the field of valves for sealing an opening between chambers, particularly chambers in a vacuum coating apparatus.
High speed vacuum coating apparatus frequently comprises a series of in-line chambers which can be separately evacuated. Such apparatus may comprise entrance lock and holding or process chambers connected by gate valves which open to allow substrates to pass from one chamber to the next. Processing of large substrates requires use of large chambers and large gate valves. Minimization of the size of such chambers is important to minimize their cost and their evacuation time, which is frequently a major factor in determining the overall processing time.
Several types of gate valves are known. Sometimes the gate is directly connected to an actuator which moves the gate along a line perpendicular to the direction of motion of the substrates as in U.S. Pat. No. 3,656,454 to Shrader. U.S. Pat. No. 3,641,973 to Shrader shows a gate valve in which the gate has four wheels which roll along a horizontal track. In other cases, a pivoted gate is connected to an actuator by suitable connecting links. U.S. Pat. No. 4,065,097 to Timin discloses a slit valve having a gate which rotates approximately 90.degree. about a pivot and having a pair of links connecting the center of each lateral edge of the gate to a cross bar attached to the end of the piston rod of a pneumatic cylinder. The cross bar is fitted with two pairs of wheels which move along a linear path confined by a track having a channel just wider than the diameter of the wheels. The movement of the actuator rod is along a line perpendicular to the direction of substrate motion through the valve opening. Such design requires either a valve having a dimension sufficient to accommodate the travel of the actuator or else an opening in the valve body to allow the actuator to protrude from the chamber with the attendant possibility of leakage around the seal of the opening.